I have made some changes to the GHC source code (6.0.1) and I would really welcome your feedback, whether they are ok for my task (first step: introduce record expressions of the shape 'struct {x1=e1,x2=e2,...,xn=en}'):

* added

("struct", ITstruct, bit glaExtsBit),

to ghcExtensionKeywordsFM and ITstruct to Token in Lex.lhs

GHC's lexer is now based on an Alex specification, so this will be different in future GHCs.

'struct' { ITstruct }

to the token part of Parser.y (please tell me, why in the lexer we declare ITstruct to represent the keyword "struct" and in the parser specification we turn back to 'struct'),

In the parser 'struct' is just a token used in the grammar file, it doesn't represent an actual Haskell string.

How can I speed up the recompilation process? I just want to check, whether my changes are compilable or not, is it possible to switch off optimization and other time consuming transformations?

You should definitely turn off optimisation when developing GHC. The Building Guide describes how to do this: http://www.haskell.org/ghc/docs/latest/html/building/building-guide.html Cheers, Simon